Drill point gauge



May 20, 1952 T. CUFF 2,597,300

DRILL POINT GAUGE Filed May 3, 1948 /2/6 Alva.

Patented May 20, 1952 UNITED STATES PATENT QFFICE DRILL POINT GAUGE Thomas Gulf, Saskatoon, Saskatchewan, Canada Application May 3, 1948, Serial No. 24,889

1 Claim. 1

My invention relates to new and useful improvements in drill point gauges, an object of the invention being to provide a device of the character herewithin described whereby the accurate grinding of drills is facilitated.

A further object of the invention is to provide a device of the character herewithin described which incorporates an adjustable protractor gauge thereby permitting the cutting faces of twist drills to be ground at the desired angle.

Another object of the invention is to provide a device of the character herewithin described which incorporates an adjustable drill point indicator, whereby the drill point may readily be maintained on the longitudinal axis of the twist drill during the sharpening operation.

A still further object of my invention is to provide a device of the character herewithin described which may be attached to any standard metal rule.

A further object of my invention is to provide a device of the character herewithin described, which is convenient to use and which, due to its construction, provides an economical, accurate precision instrument.

With the foregoing objects in view, and such other objects and advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, my invention consists essentially in the arrangement and construction of parts all as hereinafter more particularly described, reference being had to the accompanying drawings in which:

Figure 1 is a front elevation of my 'device mounted upon a standard rule illustrating the method of centering the drill point and gauging the cutting angle.

Figure 2 is a top plan view of my device mounted upon a standard rule.

In the drawings like characters of reference indicate corresponding parts in the different figures.

Depending upon the material being drilled, the rate of feed of the drill, and the speed of rotation thereof, the angle between the cutting edges of a twist drill or reamer may be varied considerably. However, in order to obtain the maximum cutting eificiency it is essential that the drill is provided with cutting angles that are particularly suited to the circumstances, in order to avoid the possibility of overheated or broken drills, or a rough finish to the drilled aperture. The majority of operators are unable to gauge this cutting angle accuratelyWhen sharpening the twist drill, therefore it is necessary to provide some means where- Where extremely accurate drillings are required,

it is conventional practice to utilize a drill of slightly smaller diameter than the size of aperture required, followed by the use of a reamer and it will be realized that in this instance any eccentricity of the original drilling will render the position of the subsequently reamed aperture uncertain.

Consequently I have designed my novel drill gauge in order to facilitate the accurate grinding of drills, endeavouring at the same-time to provide a device which may readily be carried in the pocket and which may be prepared for use with the minimum of delay.

Upon reference to the accompanying drawings it will be observed that my device comprises the sector plate I machined from flat stock and having the configuration best illustrated in Figure 1 of the accompanying drawings. Pivotally attached substantially towards the point of convergence 2 of the sides 3 of my sector plate is the protractor beam 4. This beam, which is in the form of a longitudinally extending and parallel strip, is provided on the opposite end thereof with the oifset quadrant arm 5 and it is desirable that these members 4 and 5 be machined from one piece of plate taking the form best illustrated in Figure 1 of the accompanying drawings. The arcuate slot 6 is provided in the quadrant arm and is engageable by the screw threaded pin I, rigidly attached to the aforementioned sector I plate I, and which, together with the knurled span of the aforementioned slot 6. 1 II of the sector plate is provided with the pro- "tuberance l2 bearing the reference line I3, and

"ZQthe scale I0 is graduated to indicate, in conjunc- -tion with the line IS, the angular relationship between what I designate as the contact side M of my protractor beam and the vertical side 15 of my sector plate. The side [4 of the protractor beam may be angulated to form the longitudinally extending lip l4 in order to increase the contactual surface thereof, thus facilitating the use of the device as will hereinafter be explained.

Extending between the ends of the protractor beam and substantially parallel with the contact edge 14 thereof is my drill point indicator guide bar l6, angulated at each end thereof to form the pins l6 whereby the guide bar is attached to the protractor beam and maintained in parallel spaced relationship therefrom. The pointer I1 is provided with a transverse drilling by which it is slidably engageable upon the guide bar, sufficient frictional interference being provided therebetween to maintain the pointer in any desired location along the length of the guide bar. The pointer has reference to the graduations on the associated scale 18 engraved along the length of the protractor beam adjacent to the contact edge thereof.

The sector plate I is removably attached to the associated rule [9 by means of the clamp assembly 20 so that the vertical edge I of the plate is coterminous with the vertical edge 21 of the rule. By this means it will be appreciated that the protractor scale is capable of indicating the angular relationship between the contact edge M of the protractor beam and the vertical edge of the rule. The clamp is comprised of the bifurcated stem 22 permanently attached to the aforementioned sector plate I and extending therefrom substantially at right angles. The distal end 23 of this stem is screw-threaded and engageable by the notched collar 24 and the knurled nut 25. The notched collar engages the edge 26 of the rule and the knurled nut may be tightened against this collar thus holding the sector plate in frictional engagement with the rule.

Having thus described my invention in detail, its method of operation will be presented.

The protractor should be adjusted upon the sector plate so that the cutting angle required on the drill is indicated by the aforementioned reference line 13 thereupon the protractor beam clamp 8 should be tightened to maintain the protractor beam in this position. The associated drill 2'! should then be placed in vertical contact with the side 2| of the rule and the cutting edge 28 offered up to the contact face M of the protractor bar, the correct positioning thereof being facilitated by the aforementioned lip E 4. The drill point indicator ll should now be moved along the scale 18 until it coincides with the point 29 of the drill. Rotation of the drill through approximately 180 degrees will check the concentricity of the drill point. The drill may now be sharpened or ground and during this process should frequently be offered up to the gauge in order that the correct cutting angle of the edges is maintained. During this operation, of course, the drill point position may readily be checked and any correction necessary may be made during the grinding process. From the foregoin it will be realized that the correct utilization of this precision instrument will facilitate the accurate grinding of drills and the simplicity of operation will encourage its use thus resulting in a substantial saving of time and material costs.

Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claim without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

What I claim as my invention is:

A drill gauge attachment for steel rules, comprising in combination a sector plate attachable against the edge of said rule, a clamp secured to and projecting from said plate at right angles to one edge thereof, said clamp comprising a bifurcated steam through which said rule may be inserted at right angles to the axis, and a clamp tightening action on the distal end of said stem operable to effect frictional cohesion between the adjacent edges of said rule and said sector plate, a protractor beam having a graduated edge, pivotally attached to said sector plate, an arcuately slotted offset quadrant arm on the free end of said beam, beam clamping means on said plate and extending through said slot, a guide bar extending between the ends of said beam and overlying same in parallel spaced relationship and a pointer drilled normal to the pointing direction and movable along said bar via said drilling, said pointer having reference to said graduations.

THOMAS CUFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 609,895 Mitchell Aug. 30, 1898 704,263 Luck July 8, 1902 1,293,248 Tintanne Feb. 4, 1919 1,402,774 LaDow Jan. 10, 1922 1,439,282 Amsden Dec, 19, 1922 1,920,537 Ward Aug. 1, 1933 2,337,819 Hofmann Dec. 28, 1943 FOREIGN PATENTS Number Country Date 559,624 Great Britain Feb. 28, 1944 606,459 Great Britain Aug. 13, 1948 OTHER REFERENCES American Machinist, May 22, 1940, page 838. 

